.png should be the sharpest quality.. so it must be something you did in photoshop? do you know what dpi is?
Saving it as a .PNG file would not have caused the blur... Did you make all of the shapes with brushes? If so, then the blur was caused by making the vector brush larger. When you make a brush larger, it looks blurry because unlike actual vector shapes, which are always precise, even when resized, a brush is not precise, it has to duplicate/extrapolate extra pixels to make itself larger, resulting in low-fidelity edges. If this is the case, then the solution would be to use actual vectors instead of brushes, or use much larger vector brushes. If these were vectors or wallpaper-scale vector brushes, then I am at a loss as to what might have caused the problem. As for actuall CnC, I agree with Kninja, the grunge text does not fit with the vector-style background. The color shceme is nice, and the text placement is good. Overall, it is a nice first background. I would definitely try to fix the blur though.